The Telegraph
Thursday , February 27 , 2014
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Sweat! Summer is here
- Weather plays game

Calcutta’s extended winter begot a summer scourge when it finally took leave of the city this week. And this is just the beginning.

The sudden discomfort has more to do with the abrupt change in weather rather than any abnormal temperature for this time of the year, say weather scientists.

The average minimum temperature last Tuesday and Wednesday was 13.2 degrees Celsius while the corresponding figure for February 25 and 26 was 20.1 — a jump of seven degrees. The average minimum temperature too has risen from 25 to 29.6 degrees Celsius.

The mercury has maintained a normal course, though. Experts said the current weather parameters were usual for a February-end in Calcutta.

“People are feeling the heat because of two major factors… a prolonged winter ensured that when the temperature returned to normal, the change seemed magnified. Two weather systems looming on the horizon have raised the city’s relative humidity, slowing down the evaporation of sweat,” said a weather scientist at the India Meteorological Department, Calcutta.

Wednesday’s maximum temperature — 30.1 degrees Celsius — was in fact a notch below normal.

The weather office determines the normal temperature based on 30-year data (1971 to 2000). Even a three-year average for February 26 shows the maximum temperature at 32.1 degrees Celsius, suggesting that the current temperature is in the normal range.

The cold North Wind and winter normally withdraw from Calcutta by the second week of February. This year was no exception but a smart shower on February 16 pulled the Celsius down to winter level while snowfall in the Himalayan states reinvigorated the fading cold wind.

Average minimum temperature
Average maximum temperature

“It was winter with a chilly wind and clouds in the sky just a week ago. Now it’s summer and you can’t do without the fan,” said Munmun Basu, a 35-year-old Entally resident.

S. Mitra, a south Calcutta college professor, said the jostle for AC trains in the Metro has begun though he didn’t mind commuting in a non-AC carriage “till the other day”.

Mitra and the lakhs of Calcuttans dependent on the city’s crowded public transport system could blame a cyclonic circulation in Chhattisgarh and a high-pressure belt over the Bay of Bengal coast for the balmy weather. The minimum relative humidity, which indicates the volume of water vapour in the air during daytime, has been ranging between 45 and 55 per cent over the past three days.

That’s quite high considering that the three-year average for February 26 has been 34.3 per cent.

“The city is currently sandwiched between two strong systems and, hence, relative humidity will naturally remain on the higher side. But the systems are likely to spawn clouds to block the sun. Else, the discomfort will increase,” an IMD official said.

The cyclonic circulation could bring rain to parts of Bengal on Friday and there’s an “outside chance” that Calcutta too might get drenched a bit. Experts warned that rain would not bring the Celsius down — like it did two Sundays ago — because the North Wind has lost its sting.

“The northerly wind was active last week in the western districts and it rushed towards Calcutta after the rain. The wind is weak now. Any fall in temperature would be moderate,” the IMD official said.